A stopcock for medical treatment is mounted at several tubes being used in medical treatment, especially liquid transfer, blood transfer, and artificial dialysis, and switches the communication and the cut off of each tube for medical treatment. In a representative three-way stopcock as such a stopcock for medical treatment, three tubes for medical treatment are mounted, and the communication and the cut off of each tube for medical treatment are switched. In general, the three-way stopcock has two inflow ports and one outflow port and is used to switch the communication and the cut off of the inflow ports and the outflow port.
The three-way stopcock is used in joining a mixture injection channel to a main flow channel and temporarily or always mixing another liquid such as liquid medicine from the mixture injection channel with a liquid such as liquid medicine flowing in the main flow channel. In this case, one inflow port and the outflow port formed in the three-way stopcock are linearly formed to form the main flow channel, and the other inflow port is installed so that it can perpendicularly or obliquely cross the main flow channel. The other inflow port is also used as the mixture injection channel.
The three-way stopcock is generally equipped with a main body and a stopcock. The main body consists of a tubular part having a cylindrical center space and three branch tube parts mounted with separation at an angle interval of 90° on the outer peripheral surface of the tubular part. The stopcock includes a columnar valve rotatably mounted in the cylindrical space formed at the center of the tubular part of the main body and a grip part connected to the end of the valve and to rotate the valve in the cylindrical space. Also, a communication flow channel wherein branch flow channels formed in each branch tube of the main body can communicate with other branch flow channels is formed in the valve. Then, with rotation of the valve in the cylindrical space, the communication and the cut off of each branch flow channel are carried out via the communication flow channel formed in the valve. Since a tube for medical treatment is mounted in each branch tube, the communication and the cut off of the tubes for medical treatment are switched by rotation of the valve.
In this three-way stopcock, recently, various investigations have been proposed in which the workability, etc., are considered. For example, in the technique described in patent publication 1, the communication flow channel formed in the valve of the three-way stopcock has a circular arc shape, three vertical channels are installed at an interval of 90° in the circular arc shaped channel, and these three vertical channels as the branch flow channels of the main body can communicate with each other. According to Japanese Kokai Patent Application No. 2003 159336, since the communication flow channel has a circular arc shape, the dead space as an internal space in which a liquid or gas remains in the valve is reduced and the liquid flowing in the inside can be smoothly circulated. Also, since the branch flow channels do not directly communicate with the circular arc shaped channel but are connected to the vertical channels connected to the circular arc shaped channel, the flow channel can be cut off by slight rotation of the valve, so that the workability is improved.
On the other hand, if the mixture injection channel is connected to the main flow channel using a three-way stopcock, and liquid medicine is mixed into the main flow channel from the mixture injection channel, the space in the flow channel for forming the mixture injection channel is irrelevant to the flow of the main flow channel and is dead space. Therefore, liquid from the mixture injection channel remains in this part. Also, air bubbles remain in the space in the flow channel for forming the mixture injection channel. It is preferable to greatly reduce the retention of liquid and air bubbles in terms of workability, etc.
In the three-way stopcock described in the above mentioned patent publication JP 2003 159336, since the communication flow channel formed in the valve has a circular arc shape, the dead space in the branch flow channel for forming the mixture injection channel is not necessarily reduced, although the dead space in the valve can be reduced. Therefore, liquid medicine and air bubbles are likely to remain in this part.